Full length cDNA will be transcribed from purified AFP mRNA and copied with E. Coli polymerase 1 to form a double-stranded hybrid (dscDNA). This hybrid will be cloned after tailing with homopolymer (dC) and annealing with (dG) tailed plasmid pBR322DNA in E. Coli vector X1176. The amplified hybrid plasmid DNA will be extracted and labelled by nick-translation or T4 polynucleotide kinase and utilized as a specific probe for screening a rat genome library for isolation and purification of the structural gene sequences for AFP. This recombinant plasmid DNA will also be linked covalently to cellulose and used for purification of AFP mRNA. Saturation and kinetic hybridization analysis will be utilized to quantitate the nuclear and cytoplasmic distribution of AFP sequences in fetal liver, Yolk Sac, transplantable hepatomas and adult liver after exposure to chemical carcinogens.